Processing speed and executive functioning in relation to off-topic verbosity among young adults and older adults

Off-topic verbosity (OTV) is a tendency towards excessive, off-topic speech and has been linked with age-related deficits in executive functioning, particularly inhibition. However, there are numerous disagreements within the literature on what constitutes OTV, and there is a further lack of investigation into alternative cognitive explanations for the link between inhibition and OTV. The purpose of this study was to investigate the speech characteristics of OTV in young and older adults as well as to examine whether variations in OTV are better explained by diminished executive functioning or processing speed, as measured by the D-KEFS Stroop test. Young adults (n = 65; age 18-28) and older adults (n = 85; age 60-98) completed the D-KEFS Color-Word Interference Test and provided verbal samples of autobiographical episodic and procedural speech. These speech samples were rated on three facets of OTV: tangentiality, egocentrism, and quantity of speech. Procedural autobiographical speech was found to best measure age cohort variations in OTV, and higher OTV was associated with poorer Stroop test performance in older adults but not in young adults. In fact, young adults only displayed associations between poorer Stroop performance and a reduction in speech quantity. Finally, processing speed deficits were more associated with increased OTV in older adults than executive functioning. These results provide support for links between age-related cognitive decline and OTV, but the results suggest that processing speed may be more implicated than executive functioning.